Wireless telemetry of phsiological signals is desirable for sports medicine, cardiac rehabilitation, and critical care monitoring, among other applications. Wireless telemetry of the electrocardiographic activity of ambulatory patients, for example, makes possible the aquisition of data representative of the degree of cardiac dysfunction while a patient is in movement and therewith provides an increased diagnostics capability and better patient care. In sports medicine applications, wireless telemetry of electrocardiographic and electromuscular signals provides data representative of the physiological conditions of strenuously exercising patients. In critical care units, wireless telemetry of the physiological conditions of critically ill patients reduces patient clutter and substantially eliminates the troublesome wire leads and connections that characterize conventional critical care monitoring units. Wireless telemetry of the physiological condition of non-human subjects such as laboratory test animals is also desirable in many situations.
Wireless telemetry systems for monitoring the physiological conditions of human and non-human subjects must provide a signal that is invariant with respect to temperature conditions, placement conditions, and other application environment variables so that reliable and repeatable data transmission is ensured. The transmitted data moreover must be as clean and noise-free as possible to provide such a high confidence level that accurate patient diagnosis therefrom can be accomplished. Such systems should additionally be capable of telemetering several signals from a subject simultaneously to provide a monitoring capability of one or more physiological conditions from one or more bodily locations. At the same time, such systems are called upon to be of comparatively light-weight and of a small size so as to enable ease of patient placement and comfortable non-obtrusive usage.